Fuel cells are devices that convert chemical energy directly into electrical energy through a chemical reaction, typically involving hydrogen and oxygen. In a fuel cell, hydrogen gas is fed into one side, while oxygen (often from the air) enters the other side. The reaction produces electricity, water, and heat, making fuel cells a clean energy source with minimal environmental impact. Fuel cells are used in various applications, including vehicles, stationary power generation, and portable electronics. They are considered a promising technology for reducing greenhouse gas emissions and dependence on fossil fuels, contributing to a more sustainable energy future.